1. Field of the Invention
The present invention relates generally to mattresses and, more particularly, to mattresses whose surface contour and support are changed by active components in the mattress.
2. Description of the Prior Art
Generally, mattresses include passive springs which support the mattress surface. When a person lies down on the mattress, the surface contour of the mattress changes as a result of the weight of the person pressing down on the mattress surface and being supported by the passive springs. Mattresses filled with a fluid, i.e., water mattresses or air mattresses, also function passively because they respond only to weight pressing down on them. For weight that is supported by passive means, the mattress exerts an upward supporting force on each portion of the person's body that is being supported. Each upward force is equal and opposite to the downward force caused by the weight directly above it. This is the essence of passive support. When a portion of the person's body is sore, however, the upward force exerted by the passive springs can aggravate the pain. In view of these considerations, it would be desirable if a mattress were provided which reduced or minimized the upward force exerted by a mattress on sore portions of a person's body. In this respect, the portion of the weight of a person's body that is not supported by those mattress portions which exert reduced upward supporting forces would be redistributed to other portions of the mattress, which would function normally (passively).
Throughout the years, a number of innovations have been developed relating to mattresses for preventing or reducing pressure-sensitive soreness in a person lying on the mattress, and the following U.S. Pat. Nos. are representative of some of those innovations: 3,340,548, 3,656,190, 4,799,276, 4,999,861, and 5,283,735. More specifically, U.S. Pat. No. 3,340,548 discloses a mattress which contains a plurality of springs therein. The compression of springs is adjusted to accommodate a person's individual pattern of firmness/softness needs for the mattress. The specific pattern of firmness/softness is manually adjusted for each person. To adjust a mattress manually for each sore portion that a person may have on one's body may be a tedious chore. Furthermore, a sleeping person cannot make manual adjustments. In this respect, it would be desirable if a mattress were provided which automatically adjusted its surface contour and support to accommodate sore portions of a person's body. Stated somewhat differently, it would be desirable if a mattress were provided which automatically adjusted its surface contour and support. This would accommodate sore portions of a person's body and allow the portions of the person's weight not supported by the mattress to be redistributed to other portions of the mattress.
U.S. Pat. No. 5,283,735 discloses a feedback system for adjusting the load bearing surface in a chair or bed. A grid of pressure sensors is used to generate data indicating an actual force distribution on the load bearing surface, such as a mattress. The actual pressure distribution is compared with a desired pressure distribution. The upward pressure is exerted by pressure exerting devices, such as inflated bags, and is adjusted so that the actual pressure distribution approaches the pre-set desired pressure distribution. Although there is a degree of automatic surface contour and support adjustment, actual physical pressure is required to be exerted on the pressure sensors by a portion of a person's body in order to generate a pressure on the pressure sensors. This means that a sore portion of the body, such as a sore back, must exert a force on a pressure sensor before the surface contour is automatically adjusted. Such a pressure-exerting requirement of a sore portion of a person's body may still cause considerable pain. In this respect, it would be desirable if a mattress were provided which does not require a sore portion of a person's body to exert a downward force on a pressure sensor in order to automatically adjust the surface contour and support of a mattress.
Furthermore, the feedback system requires that the mattress location of the sore spot on a person's body be computed from an array of pressure distribution measurements using an electronic data processor. This computation could introduce errors in determining the mattress location of the sore spot. In this respect, it would be desirable if a mattress were provided which positively and continuously identifies the exact mattress location under the sore spot on the person with little or no data processing of an array of measurements.
U.S. Pat. No. 3,656,190 discloses a body support in the form of a bed which is designed to alleviate a person's discomfort caused by bed sores. A cyclically repeated wave-like motion of the surface contour and the associated upward force distribution is carried out by using a plurality of spring-based movable elements distributed in a grid array beneath the surface. Each movable element can have its spring compression varied. The pattern of spring compression variation is predetermined and is not responsive to any particular body portion. Once a bed sore has formed, such a cyclically repeated wave-like variation in surface contour would subject the bed sore to cyclically repeated wave-like contact and pain. In this respect, it would be desirable if a mattress were provided which reduces pain engendered by bed sores by preventing the bed sores from being exposed to any contact with or upward force from the mattress, including cyclically repeated wave-like contact.
U.S. Pat. No. 4,799,276 discloses a grid array of devices (pistons) which undergo cyclic variation with respect to the upward pressure exerted by the devices on a patient in order to alleviate bed sores. The pressure exerted by the patient's body sections against their respective support pistons is constantly measured. Adjustments of pressure exerted by the pistons depends upon the measured pressures. Actual downward physical pressure is required to generate a pressure on the sensors. As stated above, it would be desirable if actual downward physical pressure on a pressure sensor were not required in order to alleviate pain engendered by bed sores or by a sore back. As also stated above, it would be desirable if the mattress prevented the bed sores or sore back from being exposed to any contact with or upward force from the mattress, including cyclically repeated contact.
U.S. Pat. No. 4,999,861 is similar to above-discussed U.S. Pat. No. 3,656,190 for a disclosure of a wave motion bed which cyclically sends waves of firmness and softness under a bed surface to alleviate bed sores. Devices which vary the firmness and softness are plates that are raised and lowered by cams. This device presents similar problems to those presented by U.S. Pat. No. 3,656,190.
Still other features would be desirable in an automatic mattress surface contour and support changing apparatus. For example, a patient may have a sore back or a burn that covers a relatively large portion of the person's body. In this respect, it would be desirable if a relatively large portion of a supporting mattress retract when a relatively large sore area approaches the mattress.
Patients with pain in the lumbar region of the lower back often sleep on an extra firm surface to minimize the upward force on their lower back. Alternatively, they may sleep with their knees and/or head elevated in order to correct the curvature of the lower spine. It would be desirable if the portion of the mattress under the lower spine retracted, as this would remove the upward force on this part of the spine and contribute to the relief of lower back pain.
Thus, while the foregoing body of prior art indicates it to be well known to use mattresses which change surface contours and supports to redistribute weight and relieve pressure on certain body parts, the prior art described above does not teach or suggest an automatic mattress surface contour and support changing apparatus which has the following combination of desirable features: (1) positively and continuously identifies the exact mattress location(s) which are under the sore portion(s) of a person's body reclining on the mattress, even if the person moves on the mattress; (2) reduces or minimizes the upward force exerted by a mattress on sore portions of a person's body; (3) automatically adjusts its top surface contour and support to accommodate sore portions of a person's body; (4) does not require a sore portion of a person's body to exert a downward pressure on a pressure sensor in order to adjust the surface contour of a mattress; (5) reduces pain engendered by bed sores by preventing the bed sores from being exposed to cyclically repeated wave-like contact with a mattress surface; (6) automatically adjusts its top surface contour and support (upward force distribution) to accommodate sore portions of a person's body so that portions of the person's weight that are not supported by the mattress are redistributed to other portions of the mattress; and (7) can provide that a relatively large portion of a supporting mattress retracts when a relatively large area on a patient approaches the mattress. The foregoing desired characteristics are provided by the unique automatic mattress surface contour and support changing apparatus of the present invention as will be made apparent from the following description thereof. Other advantages of the present invention over the prior art also will be rendered evident.